DE69129672T2 - Image capture device - Google Patents

Description

The invention relates to an image recording device, and more particularly to an image recording device with a white balance adjustment device.

US-A-4 811 086 describes an image capture device that performs either a tracking color balance adjustment in which a color balance is adjusted depending on the color component ratio of the external light, or a setting white balance adjustment in which a color balance is performed depending on a brightness signal component ratio of an image capture signal.

Document JP-A-600 74 892 relates to a video camera using a plurality of signals obtained by sampling electrical signals output by an image pickup device to achieve reproduction in an optimal white balance state.

For this purpose, the system according to this document is able to collect a plurality of consecutive image signals in a FIFO (first-in/first-out) memory, and an average value of all stored values is calculated each time a new value is stored. The average value is compared with a reference value and corresponding output signals are formed to control two Gain control circuits such that the mean value is equal to the reference value.

The publication GB-A-2 018 546 describes an adjustment display device for a television camera. In the viewfinder of the television camera, two vertically elongated areas are superimposed on the image. Both areas can be continuous or discontinuous.

Known white balance adjusting devices of image pickup devices are divided into devices with an external measuring method for performing white balance adjustment by means of an output signal of an external color measuring sensor shown in Fig. 1 and internal measuring devices (TTL device) for performing white balance adjustment in response to an output signal of an image pickup element shown in Fig. 2. Known examples are described below with reference to Figs. 1 and 2.

Fig. 1 shows a block diagram of a known outdoor measurement mode device. The device comprises an optical image pickup system 1a, a semiconductor image pickup element 1, a brightness signal processing unit 2, a color signal processing unit 3, R and B gain control units 4 and 5, differential amplifiers 6 and 7, a modulation unit 8, an adder 9, a color temperature sensor 10 and a control signal deriving unit 11. The semiconductor image pickup element 1 is an image pickup element for converting optical information into an electrical signal. The brightness signal processing circuit 2 performs appropriate processing of an output signal of the image pickup element 1 and derives therefrom a The color signal processing unit 3 performs appropriate processing of the output signal of the image pickup element 1 and derives therefrom a low frequency luminance signal YL and color signals R and B. The R and B gain control unit 4 and 5 controls the level of output signals R and B of the color signal processing unit 3 and outputs output signals R₁ and B₁. The differential amplifier 6 derives a color difference signal RY from the luminance signal YL and the color signal R₁. The differential amplifier 7 derives a color difference signal BY from the luminance signal YL and the color signal B₁. The modulation unit 8 forms a modulation signal according to the NTSC or PAL method in response to the color difference signals RY and BY. The adder 9 forms a predetermined video signal from the output signal Y of the brightness signal processing unit 2 and an output signal of the modulation unit 8. The color temperature sensor 10 comprises a color measuring sensor excluding an image pickup element for measuring a color temperature of a light source for illuminating an object. The control voltage deriving unit 11 derives a voltage for controlling the gains of the amplifiers of the R and B gain control units 4 and 5 in response to an output signal of the color temperature sensor 10.

The operation of the circuit arrangement described above is described below with reference to Fig. 1.

A Y signal is formed by the brightness signal processing unit 2 in dependence on an output signal of the image pickup element 1 and the signals YL, R and B are obtained by means of the color signal processing unit 3. A color temperature of the light source for illuminating the object is measured by means of the color temperature sensor 10, and a control voltage for application to the R and B gain control units 4 and 5 for correcting the white balance is obtained from the control voltage deriving unit 11. The R and B gain control units 4 and 5 output color signals R₁ and B₁ whose white balance is corrected. A predetermined video signal with the adjusted white balance is formed from the signals Y, YL, R₁ and B₁ by means of the differential amplifiers 6 and 7, the modulation unit 8 and the adder 9.

Fig. 2 shows a block diagram of a known TTL mode device. Blocks 1 to 9 correspond to the identical blocks in Fig. 1. Averaging units 12 and 13 comprise low-pass filters for averaging the color difference signals R-Y and B-Y and converting them into DC voltages. In response to the averaged signals of the averaging units 12 and 13, a control voltage deriving unit 14 forms a control voltage which is applied to the R and B gain control units 4 and 5 for correcting the white balance.

The operation of the TTL mode setting is described below.

The operation of blocks 1 to 9 is the same as that of Fig. 1. The signals RY and BY averaged for one frame or several frames by the averaging units 12 and 13 are fed with a specific voltage corresponding to the 0 level of the Color difference signal is compared by the control voltage deriving unit 14 to determine whether the signals RY and BY have a level greater or less than the 0 level. The control voltage deriving unit 14 outputs a control level for adjusting the signal levels of the signals RY and BY as close to the 0 level as possible. This control voltage is supplied to the R and B gain control units 4 and 5 for adjusting the white balance.

Another known system is available as a system in which a combination of the external measurement mode and the TTL mode is provided, in addition to the above-mentioned two known systems.

Fig. 3 shows a block diagram of this additional system.

According to Fig. 3, blocks 1 to 14 are identical to those of the known arrangement of Figs. 1 and 2. The control voltage derivation unit 11 is referred to as the first control voltage derivation unit, and the control voltage derivation unit 14 is referred to as the second control voltage derivation unit. Adders 27 and 28 add a control voltage of the first control voltage derivation unit 11 and a control voltage of the second control voltage derivation unit 14 in predetermined ratios. The sum voltages of the adders 27 and 28 are used to adjust the white balance.

In the known arrangements, a signal of the image recording element 1 and a signal of the color temperature sensor, which functions as a color measuring sensor 10 with Exception of the image pickup element, added in predetermined proportions to appropriately adjust the white balance.

Another white balance adjustment method is known in JP-A-63-314 424 filed by the present applicant. According to this method, two or more color measurement methods are selected by means of a detection output signal to adjust the white balance.

In the above known outdoor metering mode as shown in Fig. 1, the precision of white balance adjustment is significantly deteriorated when light sources illuminating an image pickup device body and a subject are due to a larger separation of the image pickup device body from the subject or when photographic conditions such as sunset redness (glow) are present.

In the known TTL method according to Fig. 2, the precision of the white balance adjustment is impaired because monochrome tends towards white during correction if the majority of the object area is a color area or if the majority of the full image is monochrome.

In the additional method shown in Fig. 3, the white balance adjustment effects of each of the known methods are cancelled out to deteriorate the precision, although the precision tends to improve as a result of adding the control voltages derived from the external metering mode and the TTL mode to compensate for the respective disadvantages of the known methods. In the example described in JP-A-63-314424, this Use this method only when the ambient conditions are dark. This method is not suitable for white balance adjustment when the scene is brightly lit.

It is therefore an object of the present invention to provide an image pickup device based on an inverse relationship between a distance to an object and an influence of a single-color object color, i.e. the predominance of a color in a frame, whereby appropriate white balance adjustments can be made with respect to the photographic condition, i.e. both in a photographic condition not suitable for the outdoor metering mode (for example, over long distances, changes in brightness conditions, backlight or a dark background) and in a photographic condition not suitable for the TTL mode (for example, in a single-color frame or a large influence of a single-color object color), and at the same time an appropriate effect can be achieved in both the known method and the known additional method against the elimination of the advantages.

It is a further object of the present invention to provide an image pickup apparatus based on the fact that in case of a color signal ratio such as an R/B ratio close to 1, a monochrome frame is not predominant due to the presence of all color components, ie, a monochrome component is not predominant in a frame, an appropriate white balance adjustment can be performed with respect to the photographic conditions, ie, both in a photographic condition not suitable for the outdoor metering mode (for example, when adjusting the distance, when the brightness conditions change, when there is backlight, or a dark background) and a photographic condition not suitable for the TTL mode (for example, when there is a monochrome full-frame image or a large influence of a monochrome object color), and at the same time an appropriate effect can be achieved despite eliminating the advantages of both the known methods and the known additional method.

It is a further object of the present invention to provide an image pickup device in which the above-described known problems are solved, in which an appropriate white balance adjustment can be performed with respect to the photographic conditions, i.e., in a photographic condition not suitable for the outdoor metering mode (for example, in a distance setting, in a change in the lighting conditions, in a backlight or in a dark background) as well as in a photographic condition not suitable for the TTL mode (for example, in a monochrome full-frame or a large influence of a monochrome object color), and at the same time an appropriate effect is achieved against the elimination of the advantages of both the known methods and the additional known method.

To achieve the above-mentioned object according to an embodiment of the present invention, an image recording device is provided with the features specified in claim 1.

The invention is further developed with the features according to the specified dependent claims.

With the above arrangement, the first white balance adjusting means performs white balance adjustment using the signal output from the image pickup element, and the second white balance adjusting means performs white balance adjustment using the output signal of the colorimetry sensor excluding the image pickup element. The synthesizing means variably sets the synthesizing ratio of the control signals output from the first and second white balance adjusting means. Appropriate white balance adjustment is performed using a white balance control signal synthesized by the synthesizing means, whereby an image pickup operation is performed.

When distance information of a distance measuring device for measuring a distance between the image pickup device and the object is used as information of the optical system, control signals from both white balance adjusting devices are synthesized in a predetermined ratio depending on the distance information of the distance measuring device for measuring a distance between the image pickup device and the object, whereby white balance adjustment is performed.

If the information of the optical system is formed by information of a focal length (length) from the optical image pickup system, then a synthesizing ratio of the control signals from both white balance adjusting devices is variably determined depending on the focal length information of the optical image pickup system to obtain a single control signal, thereby performing white balance adjustment.

If an optical system information is formed by an information of the distance measuring device for measuring the distance between the image pickup device and the object and a focal length information of the optical image pickup system, then the control signals of both white balance adjusting devices are synthesized by these information to obtain a single control signal, whereby an appropriate white balance is carried out.

In the above arrangement, the first white balance adjusting means performs white balance adjustment using the signal output from the image pickup element, and the second white balance adjusting means performs white balance adjustment using the signal output from the colorimetric sensor excluding the image pickup element. The synthesizing means compares the colorimetric information ratio of the image pickup element with the colorimetric information ratio of the colorimetric sensor and variably adjusts the synthesizing ratio of the signals output by the first and second white balance adjusting means. Appropriate white balance adjustment is performed using a white balance control signal synthesized by the synthesizing means, and an image pickup operation is performed.

In the arrangement including the additional warning device for generating a photographic warning signal, a photographic warning signal is generated if a white balance adjustment is not carried out in an appropriate manner.

In the arrangement including the additional storage device for storing the white balance control voltages of the first and second white balance adjusting devices, an appropriate white balance adjustment is carried out by means of the stored white balance control voltages.

According to the above arrangement, the synthesis ratio of the control signal for white balance adjustment from the first white balance adjustment means and the control signal for white balance adjustment from the second white balance adjustment means is variably adjusted by the synthesis means depending on a difference between the output signal of the image pickup element or an equivalent signal thereto and the output signal of the colorimetric sensor, thereby obtaining a single control signal for white balance adjustment. Using this control signal, appropriate white balance adjustment and image pickup operation are performed.

A large difference between the control signals indicates a large difference between a photographic condition in the image pickup element, such as an object brightness, and a photographic condition in the color measurement sensor. Using this comparison result, a White balance adjustment control signal is generated and more precise white balance control can be realized.

To achieve the above object, according to a further embodiment of the present invention, there is provided an image pickup device characterized by a first white balance adjusting means for generating a white balance control signal for white balance adjustment using a signal output from an image pickup element, a second white balance adjusting means for generating a white balance control signal for white balance adjustment using an output signal output from a color measuring sensor other than the image pickup element, and a synthesizing means for comparing the signals relating to predetermined positions on a frame after sampling signals output from at least the image pickup element and mixing the white balance control signals of the first and second white balance controlling means in a predetermined ratio depending on a comparison result.

According to the above arrangement, the image pickup outputs with respect to predetermined positions on the frame after sampling the image pickup outputs of the image pickup element are compared with each other, and white balance adjustment is performed based on the comparison result, thereby performing an image pickup operation.

The first white balance adjustment device generates the white balance control signal for white balance adjustment using the signal output from the image pickup element, and the second white balance adjusting means generates the white balance control signal for white balance adjustment using the signal output from the color measuring sensor excluding the image pickup element. The synthesizing means compares the signals corresponding to predetermined positions on the frame after sampling the signals output from at least the image pickup element, and mixes the white balance control signals of the two white balance adjusting means at a predetermined ratio depending on the comparison result, thereby achieving white balance adjustment according to the mixed output signal, thereby performing an image pickup operation.

The image capture operation can be performed with a suitable white balance level obtained with the white balance adjustment specified above.

If a warning device is provided for generating a photographic warning signal, then an image warning signal is generated depending on an image recording condition.

Further, when a memory device for storing white balance control voltages is provided, appropriate white balance adjustment is performed using the stored white balance control voltage depending on the image pickup condition, thereby performing an appropriate image pickup operation.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. In the above summary and the following detailed description, embodiments 1 to 23 (Figs. 4 to 21) are outside the scope of the independent claim and are merely examples illustrating the processing flow for selecting between different white balance adjustment devices.

SHORT DESCRIPTION OF THE CHARACTERS

Fig. 1 to 3 are block diagrams for the respective representation of known arrangements,

Fig. 4 is a block diagram illustrating the first embodiment of the present invention,

Fig. 5 is a block diagram illustrating a switching control signal deriving unit of the first embodiment,

Fig. 6 is a block diagram for illustrating the second embodiment,

Fig. 7 is a flow chart for illustrating the second embodiment,

Fig. 8 is a block diagram for illustrating the third embodiment of the present invention,

Fig. 9 is a flow chart for illustrating the third embodiment,

Fig. 10 is a block diagram for illustrating the fourth embodiment of the present invention,

Fig. 11 is a block diagram for illustrating the tenth embodiment of the present invention,

Fig. 12 is a flow chart for illustrating the tenth embodiment,

Fig. 13 is a block diagram for illustrating the twelfth embodiment of the present invention,

Fig. 14 is a block diagram for illustrating the sixteenth embodiment of the present invention,

Fig. 15 is a flow chart for illustrating the sixteenth embodiment,

Fig. 16 is a block diagram for illustrating the seventeenth embodiment of the present invention,

Fig. 17 and 18 are diagrams for illustrating a switching control signal deriving unit according to Fig. 16,

Fig. 19 is a block diagram for illustrating the eighteenth embodiment of the present invention,

Fig. 2'0 is a flow chart for illustrating the eighteenth embodiment,

Fig. 21 is a block diagram for illustrating the nineteenth embodiment of the present invention,

Fig. 22 is a block diagram for illustrating the twenty-fourth embodiment of the present invention,

Fig. 23 is a block diagram illustrating a switching control signal deriving unit,

Fig. 24 is a timing chart according to the twenty-fourth embodiment,

Fig. 25A to 25C are diagrams for illustrating sampling points in a frame,

Fig. 26 is a block diagram showing an arrangement of the twenty-fifth embodiment of the present invention,

Fig. 27 is a flowchart of the twenty-fifth embodiment,

Fig. 28 is a block diagram for illustrating the twenty-seventh embodiment of the present invention,

Fig. 29 is a block diagram for illustrating the twenty-eighth embodiment,

Fig. 30 is a block diagram illustrating a memory device, and

Fig. 31 is a block diagram for illustrating the twenty-ninth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 4 is a block diagram illustrating an image pickup device according to the first embodiment of the present invention. Blocks 1 to 14 correspond to the blocks designated by like reference numerals in the known arrangements. Image pickup light of an object is irradiated onto an image pickup element 1 through an image pickup optical system 1a. In the present embodiment, switches 15 and 16 select one of the control voltages output from the first control voltage deriving unit 14 and the second control voltage deriving unit 11, and supplies the selected control voltage to the R and B gain control units 4 and 5. In this way, a synthesizing ratio of 0:100% is made possible. A switching control signal deriving unit 17 derives a control signal for switching the switches 15 and 16. A distance measuring sensor 18 serves as an optical system for generating a Distance information for switching the switching control signal deriving unit 17.

Referring to Fig. 4, the operation of the first embodiment will be described below.

According to Fig. 4, the operation of the blocks 1 to 14 is the same as that of the blocks in the known arrangements according to Figs. 1, 2 and 3. One of the voltages output from the first control voltage deriving unit 14 and the second control voltage deriving unit 15 is selected by means of the switches 15 and 16, and the selected voltage is supplied to the R and B gain control units 4 and 5. In this case, a switching control signal for the switches 15 and 16 is derived by means of the switching control signal deriving unit 17. The distance measuring sensor 18 measures a distance between the object and the image pickup device and outputs a voltage value proportional to the distance. The switching control signal deriving unit 17 determines whether the measured distance is greater than a predetermined distance. If not, the switch control signal deriving unit 17 outputs a control signal for switching the switches 15 and 16 to the external measurement mode side, i.e., to the second control voltage deriving unit 11 side. Otherwise, the switch control signal deriving unit 17 generates a control signal for switching the switches 15 and 16 to the TTL mode side, i.e., to the first control voltage deriving unit 14 side.

Fig. 5 shows in detail the arrangement of the switching control signal deriving unit 17 including a comparator 19.

When an output signal S of the distance measuring sensor 18 is larger than a specific level E, it indicates a long distance. A high-level signal is supplied to the control unit for the switches 15 and 16 to set the switches 15 and 16 to the TTL mode side, i.e., to the side of the first control signal deriving unit 14. However, when the output signal S is smaller than the level E, it indicates a short distance, so a low-level signal is output to set the switches 15 and 16 to the external measurement mode side, i.e., to the side of the second control voltage deriving unit 11.

The image pickup element 1, the averaging units 12 and 13 using the output signal of the image pickup element 1, and the first control voltage deriving unit 14 constitute a first white balance adjusting means. The color temperature sensor 10 serving as a color measuring sensor excluding the image pickup element and the second control voltage deriving unit 11 constitute a second white balance adjusting means. The switch control signal deriving unit 17 and the switches 15 and 16 constitute a synthesizing means.

If an object is very far away and the influence of the object color is small, then according to the arrangement and operation described above, the TTL mode is set using the first white balance adjustment device, which is not suitable for white balance control of a monochrome full-frame image. However, if the object is close and the influence of the object color is large, then the second white balance adjustment device is used to Outdoor metering mode is set, with appropriate white balance adjustment performed.

Since the distance measuring sensor 18 is provided in addition to the image pickup optical system 1a, distance information can be obtained without increasing the complexity of the image pickup optical system 1a. In this case, both white balance adjusting means can be used selectively.

In the present embodiment, the switches 15 and 16 for switching the synthesis ratio between 0% and 100% are used as the synthesis means in the present invention. However, a mixer for continuously or stepwise changing the synthesis ratio depending on the distance information may be used. In this case, white balance control can be performed based on a highly accurate control signal.

Fig. 6 is a block diagram of an image pickup device according to the second embodiment of the present invention. The blocks 1a and 1 to 16 correspond to the blocks designated by the same reference numerals in the known arrangement shown in Fig. 1. A block 19 outputs distance information between a zoom lens in the optical image pickup system 1a and its focal length, that is, distance information between the lens corresponding to the object and the image formation point. The image pickup device according to this embodiment further comprises an A/D converter 20 and a microcomputer 21.

In the second embodiment, focal length information of a zoom lens system serving as an optical system is supplied to the A/D converter 20 and the microcomputer 21 instead of the distance information of the distance measuring sensor of the first embodiment, thereby deriving a switch switching control signal.

Specifically, when the focal length is increased and when the focal length information exceeds a predetermined level (fs), a single-color object color is spread over the entire frame, and a control signal is output from the microcomputer 21 so that the switches 15 and 16 are connected to the external metering mode side. Otherwise, a control signal is output from the microcomputer 21 so that the switches 15 and 16 are set to the TTL mode side. As a result, appropriate white balance adjustment can be performed by appropriate switching as in the first embodiment.

The details of the operation of the present embodiment will be described with reference to a flowchart of Fig. 7.

In step S1, a specific value, i.e., a threshold value fs of the focal length information is set. In step S2, the focal length information is input from the zoom lens block 19 and is A/D converted, supplying digital data to the microcomputer 21.

In step S2, the focal length information is compared with the threshold value fs. If the condition f > fs is met, a high-level signal is sent to the switches 15 and 16 to select the external measurement mode side in step S4. On the other hand, when the condition f ≤ fs holds, a low level signal is output to the switches 15 and 16 to select a TTL mode side in step S5.

The circuit blocks of the first and second white balance adjusting means are the same as those of the first embodiment. The microcomputer 21 and the switches 15 and 16 constitute a selection means. Instead of the distance measuring sensor of the first embodiment, the first and second white balance adjusting means are selectively used in accordance with information of the optical system, i.e., the zoom lens serving as an image pickup lens or the device arranged (connected) together with the image pickup lens. The focal length of the image pickup zoom lens is increased and appropriate white balance adjustment can be performed even when the frame image is formed in monochrome.

Fig. 8 shows a block diagram for illustrating the third embodiment. The blocks 1a, 1 to 10, 12, 13 and 18 to 21 correspond to the blocks designated by the reference numerals 18-21 in the first and second embodiments. An image recording device according to the third embodiment also comprises A/D converters 22, 23 and 24 and a D/A converter 25.

The operation of this embodiment is described in detail below with reference to a flow chart in Fig. 9 and essentially concerns the operation of the microcomputer 21.

In step S10, threshold values (fs and ss) of the focal length and the object distance are set as shown. The focal length and the object distance are A/D converted in a photographic state in step S11 by means of the A/D converters 20 and 24. The converted digital data are read in by the microcomputer 21. In steps S12 and S13, the object distance s and the corresponding threshold value ss and the focal length f and the corresponding threshold value fs are compared with each other. If the relationships s < ss and f > fs hold, the control flow goes to step S14. Otherwise, the control flow goes to step S15. In step S14, a value obtained by A/D converting an output signal of the color temperature sensor 10 by means of the A/D converter 23 is input to the microcomputer 21. The control flow then goes to step S15, and a control voltage is derived from the input value and output from the D/A converter 25 (step S15).

In step S16, values obtained from A/D conversion by the A/D converter 22 from the output signals of the averaging units 12 and 13 are supplied to the microcomputer 21 to derive a control voltage from the input values. The control signal is input to the D/A converter 25 (step S17). An analog control voltage is output from the D/A converter 25 to the R and B gain control units 4 and 5, thereby performing white balance adjustment.

The first and second white balance adjusting means are substantially the same as those of the first embodiment except that the A/D converters 22 and 23 are used instead of the first and second Control voltage deriving units 14 and 11 are added. The microcomputer 21 forms a synthesizing device.

A white balance adjustment method is determined depending on the focal length information of the image pickup optical system and the object distance information of the optical device for selecting the first or second white balance adjustment device. This enables more appropriate and suitable white balance adjustment to be performed.

In the present embodiment, the external metering mode is set only when the object distance and the focal length exceed the threshold values (threshold levels). However, the modes can also be switched if one of the object distance and the focal length is preferably used. In this case, an image is obtained that is adapted to the needs of the person taking the photograph.

In each of the above-described embodiments, a predetermined processing is directly performed based on an output of the image pickup element 1. However, an output of the image pickup element 1 may be once stored in an image memory as a frame memory 26 as shown in Fig. 10, and the predetermined processing may be performed based on the output of the image memory. In this case, processing in units of frames can be easily performed, and an improvement in accuracy can be expected.

In the above embodiment, the signals R-Y and B-Y of the color signal are obtained as signals of the image pickup element when used in the first white balance adjusting means. However, in the fifth embodiment, color signals R, G and B are used instead of the color difference signals. In this case, further improvement of the white balance adjusting effect can be achieved. As shown by a broken line in Fig. 7, the color signals R and B are extracted from the R and B gain control units 4 and 5.

In the above embodiment, a control signal is obtained as a signal for use in the first white balance adjusting means by averaging the color signal over the entire frame in the TTL mode. In the sixteenth embodiment, however, another method of obtaining a control signal using only the color signal of the luminance components with high luminance is used.

In the above embodiment, the first or second white balance adjusting means is selected for obtaining a control voltage for the TTL or external metering mode. However, in the seventh embodiment, an average value or a value near the average value of the control voltages of both modes is used near a switching threshold in consideration of both control voltages, and the control voltages are gradually changed. In this case, a more stable image pickup operation can be performed with a value near the threshold.

In an eighth embodiment, in order to prevent unstable operation near the threshold value (threshold level), a hysteresis characteristic may be provided to the information level determining means of the optical system (for example, a comparator and microcomputer comparison operations). In this case, a more stable image pickup operation can be performed with a value near the threshold value.

Distance measurement information according to the ninth embodiment can be obtained by means of a device for detecting a focusing position (focus position) in response to an output signal of an image pickup element.

In each embodiment as described above, the synthesizing ratio of the control signal output from the first white balance adjusting means based on the output signal of the image pickup element and the control signal output from the second white balance adjusting means based on the color temperature sensor other than the image pickup element is variably controlled depending on the information of the optical system, and white balance adjustment is performed based on the variable output signal. Therefore, an image pickup apparatus is provided in which appropriate white balance adjustment can be performed with respect to photographic conditions, that is, with respect to a photographic condition not suitable for an outdoor measuring mode (for example, a distance adjustment, when the lighting condition changes, when the light is backlit, or when the background is dark) and a photographic condition which is not suitable for the TTL mode (for example, in a monochrome full image or a large influence of a monochrome object color), and at the same time an appropriate effect is achieved despite eliminating the advantages of both the known methods and the additional known method.

According to the present invention, when the synthesis ratio of the white balance control signals is controlled in a variable manner in particular depending on the distance information, this distance information can be obtained by means of a general autofocus device. The distance measuring device need not be provided separately only for the white balance. Thus, a compact device with effective use of the autofocus device can be achieved as a whole.

If the distance information is obtained from the optical device for measuring a distance between the image pickup device and the object, the distance information can be obtained without complicating the optical image pickup system. The control signals of the two white balance adjusting devices can be adjusted appropriately and variably by the distance information, so that appropriate white balance adjustment can be performed.

When the distance information is formed by the focal length information of the optical image pickup system, the focal length of the zoom lens of the optical image pickup system is increased and the entire frame image is formed in monochrome, whereby the second white balance adjusting device is operated.

Otherwise, the first white balance adjustment device is operated, which always ensures an appropriate white balance adjustment.

If the distance information is obtained from information of an optical device for measuring a distance between the image pickup device and the object and the focal length information of the optical image pickup system, then an image pickup device is present that is capable of performing an appropriate and suitable white balance adjustment including the effects of the arrangement described above.

According to the present embodiment, since the distance information is used, it is possible to solely determine whether a frame is a monochrome frame, regardless of the brightness and colors of the object, whereby accurate white balance control can be performed.

Fig. 11 is a block diagram of an image pickup device according to the tenth embodiment of the present invention. Blocks 1 to 12 correspond to the blocks designated by like reference numerals in the known arrangements. The image pickup device according to the tenth embodiment further comprises a microcomputer 113, averaging units 114 and 115 for averaging the R and B signals of one frame to several frames, A/D converters 116, 117 and 118, and a D/A converter 119. Fig. 12 shows a flow chart for illustrating the operation of the tenth embodiment.

In this embodiment, the image pickup element 1, the averaging units 11 and 12 and the A/D converter 117 form a first White balance adjusting means. The color temperature sensor 10 serving as a color measuring sensor excluding the image pickup element and the A/D converter 116 constitute a second white balance adjusting means. The microcomputer 113 constitutes a synthesizing means.

The microcomputer 113 switches the synthesizing ratio of the control signals output from the first and second white balance adjusting means between 0% and 100%. This means that one of the control signals of the first and second white balance adjusting means is selected and output.

Fig. 12 shows a flow chart to illustrate an operation of the microcomputer 113.

The operation of the tenth embodiment will now be described with reference to Figs. 11 and 12. The operation of blocks 1 to 12 is the same as that of the blocks of the known arrangements according to Figs. 1 to 3.

Output signals R and B of one frame to several frames of the color signal processing unit 3 are averaged by the averaging means 114 and 115. The averaged values are supplied to an A/D converter 118, and the A/D converter 118 outputs digital signals RD and BD. An output signal CC (a ratio RC/BC as a ratio of a red component to a blue component of the light of a light source obtained from the color temperature sensor) of the color temperature sensor 10 serving as a color measuring sensor other than the image pickup element is also A/D-converted by the A/D converter 118, and the signal CCD is output. In Fig. 12, in In step S20, the value C₀ = 0 is set as the initial value condition. The microcomputer 113 receives the output signals CCD, R₀, and BD from the A/D converter 118 in steps S21 and S22. In step S23, the signal CD = RD/BD is calculated. In step S23, the signal CD' = RD/BD is calculated. In step S24, the value CD' = CD - 1 is calculated. In step S25, the value CCD' = CCD - 1 + C₀ is calculated. Under the condition C₀ = 0 as the initial state, the relationship CCD' = CCD - 1 holds. In step S26, C' is compared with Cc'. If CD'<CCD' holds, outputs of the RY and BY averaging units 11 and 12 are A/D converted by the A/D converter 117 in step S27. The digital data is input to the microcomputer 113. In step S28, a white balance control voltage is derived from the input values and is supplied to the D/A converter 119 in step S28. Thereafter, in step S29, C₀ = 0.2 is set and the control flow returns to step S21. However, if CD'>CCD' holds in step S26, a control voltage is derived from the color temperature output CCD in step S30. This control voltage is supplied to the D/A converter 119. In step S31, C₀ = -0.2 is set and the control flow returns to step S21.

In this case, the value C�0 is switched between the values 0.2 and -0.2 to provide a hysteresis characteristic. As a result, under the condition of CD' ∼ CCD', i.e., if a value is close to the threshold value, the white balance method is not easily changed and the visibility (readability) is not significantly deteriorated.

As described above, with respect to the ratios R/B and RC/BC of the image pickup output signals R and B and the color temperature sensor output signals RC and BC, if the ratio R/B is closer to 1 than the ratio RC/BC, that is, if an influence of an object color is small, the first white balance adjusting means is selected to set the TTL mode, which is not suitable for white balance control of a monochrome frame. On the other hand, if the ratio RC/BC is closer to 1 than the ratio R/B, the second white balance adjusting means is selected to set the outdoor metering mode, whereby white balance adjustment is always performed.

The values 0.2 and -0.2 of C0 may be replaced by other values to achieve a degree of hysteresis for a particular image pickup purpose. The switching operation of the present embodiment may be performed when the ratio RC/BC or the ratio R/B is outside a predetermined range of 2 or more to less than 0.5. In this case, even if a large error occurs in either of these ratios due to the influence of an object color, white balance adjustment can be performed by eliminating the large difference. As a result, a desired image pickup result can be obtained.

In the present embodiment, the control signals of the white balance adjusting means are used selectively. However, the control signals may also be used to change the synthesizing ratio in a continuous or stepwise manner, with white balance control on based on a control signal with greater accuracy.

According to the eleventh embodiment as a modification of the tenth embodiment, signals RC/GC and BC/GC indicating the ratios of red to green and blue to green can be obtained from the color temperature sensor 10, the signals R, G and B can also be obtained from the color signal processing unit 3, and signals R/G and B/G can be input to the microcomputer 13 for comparison with each other, whereby a relationship between one of the output signals and the white balance control signal output can be determined. In particular, in this case, if both the ratios of red to green and blue to green are greater than 1, then the image is not influenced by a light source but by the color of the object. If such a value is detected, that is, if the detection element, for example the color temperature sensor 10 detects the conditions RC/GC>1 and BC/GC>1, then output signals of the image pickup element 1, that is, if the color of the object is greater than 1, then the ... i.e., the averaged signals R-Y and B-Y are selected to derive a control voltage. In detail, white balance adjustment is carried out by means of a control signal of the first white balance adjustment device to eliminate the influence of the object color with high accuracy.

In the above embodiment, a predetermined process is directly performed on an output signal of the image pickup element 1. However, an output signal of the image pickup element 1 may be stored once in an image memory as a frame memory 120 according to the twelfth embodiment shown in Fig. 11, and the predetermined processing may be performed on the output of the image memory. In this case, processing in units of frames can be easily performed, and an improvement in accuracy can be expected.

In the tenth to twelfth embodiments, the R-Y and B-Y signals are used as color signals, which are used in the first white balance adjusting means. In the thirteenth embodiment, the R, G and B color signals are used as color signals.

In this case, the effectiveness of the white balance adjustment can be further improved.

In the first to thirteenth embodiments, a control signal used as a signal in the first white balance adjusting means is obtained by averaging the color signals of the entire frame in the TTL mode. In the fourteenth embodiment, on the other hand, another method of obtaining a control signal using only the luminance signal of a luminance component having high luminance is used.

In the tenth to fourteenth embodiments, the first or second white balance adjusting means is selected to obtain a control voltage of a TTL or external metering mode. In the fifteenth embodiment, however, values are selected taking into account both control voltages such as an average value or a value close to the average value of the control voltage of both modes. a switching threshold value, whereby the control voltages are gradually changed.

In this case, a more stable image acquisition process can be performed with a value close to the threshold.

In the eleventh to fifteenth embodiments, a white balance cannot often be adjusted in the optimal manner when a ratio of three primary color components of each of the color temperature sensor 10 and the image pickup element 1 is approximately equal to 1. In the sixteenth embodiment, a warning signal is output or a voltage corresponding to a scene that does not satisfy the above condition is stored.

Figs. 14 and 15 show the sixteenth embodiment.

The same reference numerals as in the previous figures denote similar parts in Fig. 14. A microcomputer 121 serves as a synthesizing means including a memory 127 serving as a storage means. A warning means 122 generates a photographic warning signal. The operation of blocks 1 to 118 is the same as that of the blocks of the tenth embodiment shown in Fig. 11. The operation of the microcomputer 121 will be described below with reference to a flow chart shown in Fig. 15. The main control flow in Fig. 15 is the same as that of the tenth embodiment shown in Fig. 12 except for steps S48 and S50. Here, in steps S48 and S50, a storage value of a derived white balance control voltage is stored in the nonvolatile memory 127 in the microcomputer 121 at steps S28 and S30 in the tenth embodiment shown in Fig. 12. In the sub-flow after CD = RD/BD is derived at step S43, the relationships CD ≥ 2, CD < 0.5, CCD 2 and CCD < 0.5 are confirmed at steps S52 to S55. If any of these conditions is determined to be NO, the control flow goes to the main flow at step S44 and white balance adjustment is performed in the same manner as in the tenth embodiment. If all of the conditions are determined to be YES, the control flow goes to step S56. At step S56, the microcomputer 121 sends a warning signal E to the warning device 122 and a warning is performed. In step S57, the white balance control voltage stored in steps S48 and S50 is output to the D/A converter 119 to perform white balance adjustment.

If a difference between each of the output signals of the image pickup element 1 and the color temperature sensor 10 and a value of "1" is larger (for example, 2 or larger, or smaller than 0.5), a warning signal is output. If the difference is 0.5 or more but smaller than 2, a white balance control voltage is used to perform white balance adjustment. However, other values other than 2 or 0.5 may be used.

White balance adjustment can be performed based on the memory of the image capture device under special conditions. In addition, this special condition can be known to the warning device.

According to the above description in connection with the embodiments 10 to 16, the synthesizing ratio of the control signal of the first white balance adjusting means based on the signal output from the image pickup element and the control signal of the second white balance adjusting means based on the signal output from the colorimetric sensor other than the image pickup element is variably outputted depending on a comparison between the colorimetric information ratio of the image pickup element and the colorimetric information ratio of the colorimetric sensor. White balance adjustment and image pickup are performed. There is provided an image pickup device in which white balance adjustment can be performed with respect to photographic conditions, i.e. both in a photographic condition not suitable for the outdoor metering mode (for example, in a distance setting, in a change in the lighting conditions, in a backlight and in a dark background) and in a photographic condition not suitable for the TTL mode (for example, in an image recording frame formed in a single color and the difference between the R/B ratio and 1 is large), and at the same time an appropriate effect can be obtained despite the elimination of the advantages of both the known methods and the additional known method.

If a warning device is provided for generating a photographic warning signal and a ratio of the three primary color components of the image pickup element and the color measuring sensor other than the image pickup element is large in difference from 1, and a If satisfactory white balance adjustment is not performed correctly, a warning signal is generated to alert the user of an abnormal condition.

Further, if a storage device is provided for storing the white balance control voltages of the first and second white balance adjusting devices, and white balance adjustment is performed depending on the stored white balance control voltages, and then white balance adjustment is not performed correctly, then white balance adjustment can be performed using the white balance control voltages stored in the storage device.

According to the above description, an image recording device is thus provided which is capable of making an optimal white balance adjustment under different conditions.

Fig. 16 shows a block diagram of an image pickup device according to the seventeenth embodiment of the present invention.

Blocks 1 to 14 correspond to those of the known arrangements, which are designated by the same reference numerals.

Image pickup light is incident on the image pickup element 1 through an image pickup optical system 1a. An image pickup angle is appropriately adjusted by means of the image pickup optical system 1a. A switch control signal deriving unit 317 derives a signal for switching switches 315 and 316. A Photometry sensor 318 measures the brightness of an object. A color temperature sensor 10 serves as a color measurement sensor and is arranged independently of the optical image recording system 1a.

An optical device such as a white dispersion plate 10a (white diffusion plate) is arranged in front of the color temperature sensor 10 so that an image angle of the sensor 10 is larger than an image pickup angle of the image pickup optical system 1a. Since the image pickup light incident on the photometric sensor 318 through the image pickup optical system 1a is picked out by, for example, a semi-transparent mirror, the image angle of the sensor 318 is set to be a photometric image angle approximately equal to the image pickup angle of the image pickup optical system 1a. Brightness information within the image pickup range of the object can be outputted accurately. The photometric image angle of the sensor 318 can be set to a smaller value compared to the image pickup image angle.

Fig. 17 is a block diagram illustrating the switch control signal deriving unit 317 including a comparator 319 and an adder 320.

The image pickup element 1, the averaging units 12 and 13, and the control voltage deriving unit 14 constitute a first white balance adjusting means, and the color temperature sensor 10 serving as a color measuring sensor excluding the image pickup element and the control voltage deriving unit 11 constitute a second white balance adjusting means. The switch control signal deriving unit 317 and the switches 315 and 316 constitute a synthesizing means.

The synthesis ratio of the control signals of the adaptation device in the synthesis device is variable between 0% and 100%.

The operation of this embodiment is described below.

According to Fig. 16, the operation of the blocks 1 to 16 is the same as that of the known arrangements. The switching control signal deriving unit 317 receives an output signal Y of the photometry sensor 318 and a signal Y~ indicating the brightness information of the output signals of the color temperature sensor 10. The signal Y~ is an output signal corresponding to the green component of the light source beam or a signal obtained by mixing the components of red, blue and green in a predetermined ratio.

As described above, the angles of view of the color temperature sensor 10 and the photometric sensor 318 are different from each other. If an output of the color temperature sensor 10 has a large difference with respect to the output of the photometric sensor 318, it is considered that light incident on the object and light incident on the image pickup device are from different light sources. In this case, the output of the switch control signal deriving unit 317 is set in the following manner. The switches 315 and 316 are connected to the first white balance adjusting means and set to the TTL mode side, and the white balance control is performed based on the image pickup light of the object. However, if the difference between the outputs of the color temperature sensor 10 and the photometry sensor 318 within a predetermined range, then the switches 315 and 316 are switched to select the second white balance adjusting means in connection with an outdoor measurement mode side.

The operation of the switching control signal deriving unit 317 will be described below with reference to Fig. 17. The photometry sensor output signal Y is supplied to the non-inverting input terminal of the comparator 319, and a value YC + E obtained by adding the specific value E to the color temperature sensor output signal Yc is supplied to the inverting input terminal of the comparator 319.

If the following condition applies:

Y > YC + E

then the output signal of the switching control signal deriving unit 317 is set to a high level.

However, the following condition applies:

Y < YC + E

then the output signal is set to a low level.

When the output signal of the switching control signal deriving unit 317 is set to a high level, the switches 315 and 316 select the TTL mode side as the first white balance adjustment device, ie the However, when the output of the switching control signal deriving unit 317 is set to a low level, the external measurement mode side is selected as the second white balance adjusting means, ie, the output of the control signal deriving unit 11 for performing the white balance adjustment.

Another arrangement of the switching control signal deriving unit 317 will be described below with reference to Fig. 18. The switching control signal deriving unit 317 comprises a comparator 321 identical to the comparator 319 described above, an adder 322 identical to the adder 320 described above, a NAND gate 323 and an inverter 324.

In this case, the following condition is met:

YC - E < Y < YC + E

then an output signal of the inverter 24 is set to a low level and the second white balance adjustment device is selected. However, the following condition applies:

YC - E > Y or YC + E < Y

then the output signal of the inverter 24 is set to a high level and the first white balance adjusting device is selected.

In this arrangement, under the conditions YC - E ∼ Y or YC + E ∼ Y, the change frequency of the processes is increased and the comparators 319 and 321 can have a hysteresis characteristic.

According to the above arrangement and its operation, the control signal of the first white balance adjusting means is selected when an object and an image pickup device are adversely illuminated by another light source such as a distant object or backlight or when the object brightness is different from the ambient brightness to obtain a large output signal from the photometry sensor. When the object and the image pickup device are illuminated by a single light source or the object brightness is equal to the ambient brightness, the control signal of the second white balance adjusting means is selected to perform white balance adjustment. Therefore, appropriate white balance adjustment can be performed even under different lighting conditions.

If the incident angle of the photometry sensor 318 is set equal to or larger than the incident angle of the optical image pickup system 1a, then an image pickup device having a more appropriate white balance adjustment effect can be provided.

If a hysteresis characteristic is provided at the switching operation point between the first and second white balance adjusting means, a stable white balance adjustment control signal can be obtained in the vicinity of the switching point, thereby achieving a stable image pickup operation.

Fig. 19 is a block diagram of an image pickup device according to the eighteenth embodiment of the present invention. Blocks 1a, 1 to 10, 12, 13 and 318 correspond to those designated by like reference numerals in the seventeenth embodiment shown in Fig. 16. The image pickup device further comprises A/D converters 325, 326 and 327, a D/A converter 328 and a microcomputer 329. The image pickup element 1, the averaging circuits 12 and 13 and the A/D converter 326 constitute a first white balance adjusting means, and the color temperature sensor 10 serving as a color measuring sensor excluding the image pickup element and the A/D converter 325 constitute a second white balance adjusting means. The microcomputer 329 constitutes a synthesizing means.

Fig. 20 is a block diagram showing the operation of the microcomputer 329 shown in Fig. 19. An operation of the eighteenth embodiment will be described below with reference to Figs. 19 and 20.

A threshold value (threshold level) for level determination is set as E = E₁ in step S60. An output signal YC of the color temperature sensor 10 and an output signal Y of the photometry sensor 318 are converted into digital data by the A/D converters 325 and 326, respectively. These digital data are then input to the microcomputer 329 (step S61). In steps S62 and S63, the conditions Y < YC + E and Y > YC - E are checked, respectively. When the answer is YES in both cases in the check in steps S62 and S63, the control flow goes to step S64. An output signal CC of the color temperature sensor 10 is converted into digital data In step S65, a white balance control signal voltage is derived from the output signal CC and supplied to the D/A converter 328. In step S66, the condition E = E₂ (where E₂ > E₁) is established.

If Y ≥ Yc + E or Y ≤ YC - E is satisfied in step S62 or S63, the control flow goes to step S67. In this step, the output signals of the averaging units 12 and 13 are A/D converted and the digital data are input to the microcomputer 329. The microcomputer 329 generates a white balance control signal voltage and outputs it to the D/A converter 328. Further, the condition E = E₃ (where E₃ < E₁) is set. The signals input to the D/A converter 328 are converted into analog signals. These analog signals are supplied to the R and B gain control units 4 and 5 to perform appropriate white balance adjustment.

If there is a large difference between the output signal Y of the photometry sensor 318 and the brightness information output signal YC of the color temperature sensor 10, the first white balance adjusting means is selected. However, if Y is close to YC, the second white balance adjusting means is selected to perform the white balance adjustment. At the same time, the condition E₂ > E₁ > E₃ is satisfied. Even if an absolute value Y - YC is variable near E₁, E₂ or E₃, a hysteresis characteristic can be provided so that no influence is exerted on the selection of the white balance method. Therefore, near the switching point between the first and second White balance adjustment device to perform stable white balance adjustment.

In the seventeenth and eighteenth embodiments, predetermined processing is directly performed based on the output signal of the image pickup element 1. In the nineteenth embodiment, on the other hand, an output signal of the image pickup element 1 is stored in an image memory and the predetermined processing can be performed based on the read value. Fig. 21 shows a frame memory 330 in the nineteenth embodiment. In this case, processing in units of frames can be easily performed and an improvement in the accuracy of white balance adjustment can be expected.

In the seventeenth to nineteenth embodiments, the signals R-Y and B-Y are used as color signals in the first white balance adjusting means. However, in the twentieth embodiment, the signals R, G and B are used as such color signals. In this case, further improvement of the white balance adjusting effect is expected.

In the seventeenth to twenty embodiments, color signals of the entire frame are averaged in the TTL method to obtain a control signal as a signal for use in the first white balance adjusting means. In a twenty-first embodiment, another method of obtaining a control signal using only color signals and brightness areas of high brightness is used. In the seventeenth to twenty-one embodiments, the selection of the first or second White balance adjusting means by selecting a control signal voltage of the TTL mode or external measurement mode. However, in a twenty-second embodiment, values considering both control voltages such as an average value or a value near the average value of the control voltages of both modes are used near the switching threshold value, thereby gradually changing the control voltages.

The above value is not limited to a value in the vicinity of the threshold value. Each control signal voltage may be composed according to a predetermined ratio over the entire range of control signal voltages.

In the seventeenth to twenty-second embodiments, a photometric sensor is used independently of the image pickup optical system. However, in a twenty-third embodiment, an image pickup element is used as a photometric sensor.

In each of the above-described embodiments, the synthesizing ratio by the synthesizing device according to the present invention is variable in a range of 0% to 100%, and each control signal is output in a selective manner. However, the synthesizing ratio may be varied in a continuous or stepwise manner.

In each of the embodiments described above, the color measurement angle of the color measurement sensor is larger than that of the image pickup element, however, the color measurement angle of the image pickup element may also be larger than that of the color measurement sensor.

In the above embodiment, the photometric sensor 318 is arranged independently of the image pickup element 1. Of course, however, a brightness output signal of the image pickup element 1 can be used as an output signal of the photometric sensor 318.

As described above with respect to the seventeenth to twenty-third embodiments, the synthesizing ratio of the white balance adjustment control signal generated by the first white balance adjusting means using the signal output from the image pickup element and the white balance adjustment control signal generated by the second white balance adjusting means using the output signal of the colorimetric sensor is determined depending on the difference between the signal of the image pickup element or an equivalent signal thereto and the output signal of the colorimetric sensor, thereby obtaining a single white balance adjustment control signal. Appropriate white balance adjustment is performed using this control signal and an image pickup operation is performed. Thus, an image pickup device is provided in which white balance adjustment can be performed with respect to the photographic condition, ie both a photographic condition not suitable for an outdoor metering mode (for example, during distance adjustment, changes in lighting conditions, backlight or a dark background) and a photographic condition not suitable for the TTL mode (for example, a monochrome full frame or a large influence of a monochrome object color), and at the same time, an appropriate effect is achieved as opposed to eliminating the advantages of both the known methods and the additional known method.

According to the present invention, a desired detection can be performed accurately regardless of the colors of the object, the object brightness and the object distance. In this way, accurate white balance control is ensured.

If the angle of incidence (angle of incidence) of the photometry sensor is set to be equal to or smaller than that of the image pickup optical system, an image pickup device with a more appropriate white balance adjustment effect is provided.

Fig. 22 is a block diagram of an image pickup device according to the twenty-fourth embodiment of the present invention. This embodiment of Fig. 22 denotes the first embodiment covered by the independent claim. In this embodiment, a control signal of the present invention is used to switch between the first and second white balance adjusting means. In Fig. 22, blocks 1 to 14 correspond to those blocks provided with like reference numerals in the known arrangements. The pickup device of this embodiment comprises switches 415 and 416 for selecting a white balance control voltage from the control voltage deriving units 11 or 14 and for supplying the selected voltage to the R and B gain control units 4 and 5. A switch control signal deriving unit 417 compares (R-Y) signals from predetermined positions within a frame and compares (BY) signals from predetermined Positions within the frame using the output signals (RY) and (BY) of the various amplifiers 6 and 7 and a predetermined pulse to generate and derive a control signal for switching the switches 415 and 416. A pulse generator 418 generates a predetermined pulse, that is, a sampling pulse, which is transmitted to the switching control signal deriving unit 417. The image pickup element 1, the averaging units 12 and 13, and the control voltage deriving unit 14 constitute a first white balance adjusting means, and the color temperature sensor 10 serving as a color measuring sensor except for the image pickup element, and the control voltage deriving unit 11 constitute a second white balance adjusting means. The switching control signal deriving unit 417, the switches 415 and 416, and the pulse generator 418 constitute a synthesizer serving as a control means.

In the present embodiment, the synthesizing means selectively outputs a white balance control signal output from each white balance adjusting means. Specifically, the synthesizing means switches the synthesizing ratio between 0% and 100%.

Fig. 23 is a block diagram showing an arrangement of the switching control signal deriving unit 417 shown in Fig. 22. The switching control signal deriving unit 417 comprises adders AD1 to AD8, comparators CP1 to CP8, NAND gates ND1 to ND6, NOR gates NR1 to NR3, a standard voltage source E and a sample hold circuit 19-1. An arrangement for an operation of inputting the BY signal from the differential amplifier 7 to another sample hold circuit 19-2, to an operation for outputting a signal to the NAND gate ND6 is identical to that from an operation for processing the RY signal to an operation for inputting a signal to the NAND gate ND5, and a detailed description is therefore omitted.

Fig. 24 is a timing chart for illustrating this embodiment, and Figs. 25A to 25C are diagrams for illustrating the sampling points within the frame.

The operation of the twenty-fourth embodiment will be described with reference to Figs. 22 to 25C.

According to Fig. 22, the operation of the blocks 1 to 14 corresponds to that of the blocks of the known arrangement, which are designated by the same reference numerals. One of the white balance control voltages derived from the control voltage deriving units 11 and 14 is selected by means of the switches 415 and 416, and the selected control signal is supplied to the R and B gain control units 4 and 5. A switching control signal for the switches 415 and 416 is formed by means of the switching control signal deriving unit 417 from the output signals R-Y and B-Y of the differential amplifiers 6 and 7 and a pulse of the pulse generator 418.

The operation of the switching control signal deriving unit 417 will be described in detail below with reference to Figs. 23 and 24.

The output signal R-Y ( in Fig. 24) of the differential amplifier 6 is supplied to the sample-hold circuit 19-1. The sample-hold circuit 19-1 samples the R-Y signal during the high level period of sample-hold pulses SHP1 to SHP4 (c to h in Fig. 24) sent from the pulse generator 418. During a period except for the above period, the held pulses SH1 to SH4 ( to in Fig. 24) occur.

The signals SHP1 and SHP2 in the present embodiment sample left and right R-Y signals as shown in Fig. 25A on the upper scanning line of the predetermined frame. SHP3 and SHP4 in Fig. 25A sample left and right R-Y signals on the lower scanning line of the frame. These signals SHP1 to SHP4 sample the corner signals R-Y of the frame.

The signals ~SHP1 and SHP2 and the signals SHP3 and SHP4 are arranged at the rising and falling positions in a scanning line as indicated by q and h in Fig. 24. The signals SHP1 and SHP2 may be arranged on a scanning line different from the scanning line of SHP3 and SHP4.

Pairs of derived signals SH1 to SH4 are picked out and compared with each other. For example, signals SH1 and SH2 are considered and picked out in pairs, and signal SH1 is fed to adders AD1 and AD2. Adders AD1 and AD2 are also each fed with a positive voltage E and a negative voltage -E.

Output signals of the adders AD1 and AD2 are connected to the positive terminal of the comparator CP1 and the negative terminal of the comparator CP2. The signal SH2 is connected to the negative terminal of the comparator CP1 and the positive terminal of the comparator CP2. The following condition is formed:

SH1 + E > SH2

where the comparator CP1 is set to a high level. The following condition applies:

SH1 - E < SH2

then the comparator CP2 is set to a high level. The output signals of the comparators CP1 and CP2 are fed to a NAND gate ND1. If the following condition:

SH&sub1; - E < SH2 < SH1 + E

is satisfied, the NAND gate ND1 is set to a low level. Thus, the output signal of the NAND gate ND1 is set to a low level only when a level difference between the signals SH1 and SH2 is smaller than a value corresponding to the predetermined level E.

Similarly, the output signals of the NAND gates ND2, ND3 and ND4 are set to a low level only when differences between the signals SH3 and SH4, between the signals SH2 and SH4 and between the signals SH1 and SH3 are smaller than a value corresponding to the predetermined level E.

An output signal of the NOR gate NR1 is set to a high level when both output signals of the NAND gates ND1 and ND2 are set to a low level. If both output signals of the NOR gates NR1 and NR2 are set to a high level, then the output signal of the NAND gate ND5 is set to a low level.

Thus, an output signal of the NAND gate ND5 is only set to the low level when the signals SH1 to SH4 satisfy the following conditions:

SH1 - E < SH2 < SH1 + E SH4 - E < SH3 < SH4 + E SH2 - E < SH4 < SH2 + E and SH3 - E < SH1 < SH3 + E

The sample hold pulses SHP1 to SHP4 in Fig. 24 correspond to the upper left, upper right, lower right and lower right positions in the frame in Figs. 25A to 25C, respectively, in the order given above. In the present embodiment, the strengths of the R-Y signals at the four corners are compared with each other. When the differences between the symmetrical signals, i.e., the right and left signals and the lower and upper signals are smaller than E, and when a difference between a sum of one pair of diagonal signals and the sum of the other pair of diagonal signals is smaller than 2E, an output signal of the NAND gate ND5 is set to a low level.

A similar procedure is carried out for the output signal BY of the differential amplifier 7. Only when differences between the right and left signal components and the upper and lower signal components are smaller than E and the difference between the sum of one pair of diagonal signals and the sum of the other pair of diagonal signals is less than 2E, the output signal of the NAND gate ND6 is set to a low level.

Only when both output signals of the NAND gates ND5 and ND6 are set to a low level, i.e. only when both R-Y and B-Y signals satisfy the above-mentioned conditions, an output signal of the NOR gate NR3 is set to a high level.

According to the above arrangement and operation, a difference in color or color signals of the sampling points is smaller than the predetermined value E when the output of the NOR gate NR3, i.e., the output of the switching control signal deriving unit 417 is set to a high level. In this case, the majority of the entire screen is assumed to be monochrome. This corresponds to a scene not suitable for the TTL mode. The switches 415 and 416 are connected to the external measurement mode side to provide the second white balance adjusting means. When the output of the switching control signal deriving unit 417 is set to a low level, the TTL mode side serving as the first white balance adjusting means is operated to perform white balance adjustment with high accuracy.

In this embodiment, threshold values (threshold levels) for detecting the differences between parts having a symmetrical relationship such as a horizontal relationship or a vertical relationship are set slightly larger. Detection errors can also be eliminated in the diagonal direction, which tends to to create a color level difference due to a change in light intensity caused by a shadow, even on a single object.

The first white balance adjusting means of the TTL mode or the second white balance adjusting means of the external metering mode is used selectively by comparing the color signals at predetermined sampling points on the frame, whereby an image pickup operation with an optimal white balance adjustment can always be performed.

The sampling points in the above embodiment are determined as positions near the corners of the frame, but may also be determined as central areas in the frame.

The sampling points can be set variably depending on different types of an object. For example, if a person is to be photographed, then the sampling points can be set in the central area. However, the sampling points should be arranged in corners if a scene is to be photographed.

In the twenty-fifth embodiment, the switch control signal deriving unit 417 of the twenty-fourth embodiment shown in Fig. 22 can be formed by an A/D converter and a microcomputer.

Fig. 26 is a block diagram showing the twenty-fifth embodiment. The image pickup device comprises a microcomputer 419 and an A/D converter 420. Other blocks of this embodiment are designated by the same reference numerals as those of the twenty-fourth embodiment.

The arrangements of the first and second white balance adjusting means are the same as those of the first embodiment. The A/D converter 420, the microcomputer 419, and the switches 415 and 416 constitute a selecting means.

Fig. 27 is a flow chart for illustrating the operation of this embodiment. In step S70, the A/D converter 420 samples the signals R-Y and B-Y for a predetermined period corresponding to the signals SH1 to SH4 of the first embodiment in response to an instruction from the microcomputer 19 to obtain digital signals. These digital signals are supplied to the microcomputer 419. In steps S71 to S74, the strengths of the signals SH1 to SH4 are compared with those of the signals R-Y and B-Y in response to an internal comparison instruction to check whether the signals SH1 to SH4 are within a predetermined level range. If so, the control flow goes to step S75 and a high level signal is outputted for setting the switches 415 and 416 to the control voltage deriving unit 11 side, thereby selecting the outdoor measurement mode side as the second white balance adjusting means and thereby performing an image pickup operation.

If the signals SH1 to SH4 are not within the predetermined level range, the control flow goes to step S76, and a low level signal is output to set the switches 415 and 416 to the TTL mode side as the first white balance adjusting means. A suitable White balance adjustment is performed and then an image capture process takes place.

In the twenty-fourth and twenty-fifth embodiments, the number of samples of each of the R-Y and B-Y signals and their sampling period are determined by the sample hold signals SH1 to SH4. The number of samples and sampling points can be changed. For example, as shown in Figs. 25B and 25C, the number of samples can be increased and the number of points can be effectively adjusted. The switching of the switches 415 and 416 is appropriately performed to accurately detect whether the frame is a monochrome frame and accurately correct the white balance. In contrast, if the number of samples is reduced, circuit elements and microcomputer programs can be reduced (simplified). An appropriate arrangement can be achieved by integrating a degree of requirement for the precision of white balance adjustment and other requirement specifications.

In the twenty-fourth and twenty-fifth embodiments, the sample values may be weighted and the weighted values may be compared with each other. Here, a threshold level (E in Fig. 23) may be set to be low for a difference between each SH value and each of the signals SH1 to SH9 with respect to the signal SH5 in Fig. 25C, and a threshold level for comparing the signals SH1 and SH9 may be set to be high. In this way, the threshold level is changed depending on the comparison purposes to select and determine an optimum white balance adjustment means. In As a result, for example, when a monochrome image is captured, a detection error of a distance between the sampling points can be prevented for appropriate selection of the white balance adjusting means. In the above embodiment, sampling values of each sampling cycle are compared with each other by means of the signals SH1 to SH4. In the twenty-sixth embodiment, average values of sampling values of several fields after sampling the SH points can be compared with each other.

Various points near the signals SH1 to SH4 on the frame can be sampled and averaged within one field period, and the averaged values can be compared with each other.

With the above arrangement, a stable appropriate white balance adjustment means can be selected free from an influence of random noise or the like.

In the twenty-seventh embodiment, the number of samples, sampling points and weighting can be changed according to the twenty-fourth and twenty-sixth embodiments based on the color temperature information, automatic exposure control (AE) information, distance information from an auto focus control (AF) sensor and focal length information obtained by using a zoom lens. For example, when an object is a distant object and has a long focal length, the light source for illuminating the external colorimetric sensor and the light source for illuminating the object are often separated from each other. The number of samplings is increased for selecting the first white balance adjusting means according to the TTL mode, and the sampling points are moved closer to the four corners of the frame as compared with the positions shown in Fig. 25A.

Even if an object is a distant object, the focal length is long, and the number of samplings and sampling periods are changed as shown in Fig. 25C, then good white balance correction often cannot be performed if the second white balance adjusting means of the outdoor metering mode is selected. A photographic warning signal is output in response to the control signal according to the present invention, and an optimal white balance adjusting means can be selected. Specifically, the warning signal detects an unfavorable condition.

An arrangement for this purpose is shown in the block diagram of the twenty-seventh embodiment according to Fig. 28. The same reference numerals as in the previous embodiments denote the same blocks in Fig. 28. An image pickup device according to this embodiment comprises a distance measuring sensor 421, a zoom lens 422, a counter 423, an AND gate 424, and a warning device 425.

As shown in Fig. 28, when a short distance between the distance measuring sensor 421 and an object and a long focal length of the zoom lens 422 are signaled to a pulse generator 418, a pulse supplied from the pulse generator 418 to the switching control signal deriving unit 417 is changed in such a way that the signal indicates an outer region of the frame corresponding to the scanning positions in Fig. 25C and that the number of pulses is changed from four to nine. The switching control signal deriving unit 417 forms a comparator corresponding to a pulse count value and sends a comparison result to the switches 415 and 416. A total number of pulses output by the pulse generator 418 is counted by the counter 423. When the pulse count value exceeds a predetermined value, the counter 423 outputs a high level signal to the AND gate 424. In this case, an output signal of the AND gate 424 is set to a high level when a switching control pulse of the switching control signal deriving unit 417 is set to a high level. The warning device 525 outputs a photographic warning signal in response to this high level signal.

In the twenty-seventh embodiment, in addition to generating a warning signal, white level control voltages of a scene that does not correspond to the warning situation can be stored as in the twenty-eighth embodiment.

Fig. 29 shows a block diagram of the twenty-eighth embodiment. The same reference numerals as in the previous embodiments denote the same blocks in the twenty-eighth embodiment.

Switches 426 and 427 establish a high impedance output state. Memories 428 and 429 store white balance control voltages. Fig. 30 is a diagram illustrating memories 428 and 429. A buffer 430 is provided in each of memories 428 and 429. Memories 428 or 429 further include a switch 431, a logic gate circuit 432 for generating signals to control switches 426 and 427, and memories 428 and 429.

A signal indicating difficulty in white balance adjustment as described in the twenty-seventh embodiment is generated by the logic gate circuit 432 and is supplied to the switches 426 and 427 and the memories 428 and 429. The switches 426 and 427 are normally switched to the TTL side or the external measurement mode side in accordance with the output of the logic gate circuit 432. When white balance adjustment is difficult, the switches 426 and 427 are set to the high impedance output state in accordance with the output of the logic gate circuit 432. Each of the memories 428 and 429 has an arrangement as shown in Fig. 30. In a normal photographing mode, the switch 431 is set from the output side to the input side of the buffer 430 in accordance with turning on of the power supply. When the device is turned off, the switch 431 is set to the output side of the buffer 430. In this case, the switch 431 remains connected to the output side of the buffer 430 even when the device is turned on, when a signal indicating difficulty in adjustment is sent from the logic gate circuit 432. In a normal operation, the white balance control signal derived by the TTL mode or the field measurement mode is supplied to the R and B gain control units 4 and 5. When the white balance adjustment is difficult, a white balance control voltage derived from the voltages stored in the capacitors C of the memories 428 and 429, ie the white balance control voltage with respect to a scene supplied to the R and B gain control units 4 and 5 according to the previous white balance adjustment state.

With the above arrangement and operation, even when white balance adjustment is difficult, the white balance adjustment data of the previous scene can be used according to the white balance adjustment state, and an image pickup operation can be performed.

In the twenty-fourth to twenty-eighth embodiments, white balance adjustment is directly performed with the output signal of the image pickup element 1. However, in the twenty-ninth embodiment, an output signal of the image pickup element 1 may be stored in an image memory as a frame memory 433 as shown in Fig. 31, and the white balance adjustment process may be performed with the data read out from the frame memory 433.

In this case, processing in units of frames can be simplified and an improvement in the accuracy of white balance adjustment can be expected.

In the twenty-fourth to twenty-ninth embodiments, the signals R-Y and B-Y are used as color signals in the first white balance adjusting means. However, the signals R, G, and B may be used as color signals in the thirtieth embodiment.

In this case, the white balance adjustment effect can be further improved.

In the twenty-fourth to thirty-fifth embodiments, color signals of the entire frame are averaged to obtain a white balance control signal as a signal used in the first white balance adjusting means. However, in the thirty-first embodiment, another method is used to obtain a control signal using only color signals of the luminance components having high luminance.

In the twenty-fifth embodiment, the switch control signal deriving unit 417 of the twenty-fourth embodiment shown in Fig. 22 is replaced by an A/D converter and the microcomputer 419 as shown in Fig. 26. As the thirty-second embodiment, the control voltage deriving units 11 and 14 and the switches 415 and 416 may be formed by an A/D converter, a microcomputer and a D/A converter.

In this case, the components used to form the circuit can be systematically arranged and the microcomputer functions can be used effectively.

In the twenty-fourth to thirty-second embodiments, switching is performed to select either the first or second white balance adjusting means. In a thirty-third embodiment, both control voltages may be set in terms of average values of the control voltages of both means or their approximate values in the vicinity of the switching threshold values (threshold levels) in a predetermined ratio mixed together to produce a single white balance control voltage, thereby controlling the control voltage in a continuous or stepped manner.

In this case, a stable image acquisition operation can be performed near the threshold.

The values are not limited to values close to the threshold. The control voltages of both devices can be mixed in a predetermined ratio over the entire range of signal levels.

In the twenty-fourth to thirty-three embodiments, a hysteresis characteristic may be provided for preventing unstable operation in the vicinity of the threshold level in comparison operations in the comparator of the optical system information level determining means and the microcomputer.

In this case, a more stable preferential image acquisition process can be performed near a threshold value.

According to the thirty-fourth embodiment, time constants of the averaging units (integrators) 12 and 13 can be variably controlled using the control signals according to the present invention.

In detail, the integrators forming the averaging units 12 and 13 shown in Fig. 22 may be formed by an arrangement using a personal computer or an intensity controller. These circuit components may be variably controlled depending on an output signal of the Switch control signal deriving unit 417.

For example, when the object does not change, the time constant is increased to improve the precision of the control signal output from the control voltage deriving unit 14 of the TTL mode. On the other hand, when the object moves quickly, the time constant is decreased to reduce disturbances in the white balance associated with a change in the object.

As described above, in the twenty-fourth to thirty-fourth embodiments, the control means compares image pickup output signals from predetermined positions on the frame after sampling the image pickup output signals from the image pickup element, and white balance adjustment is performed based on this comparison result. More specifically, the synthesizing means compares the signals from the predetermined positions on the frame after sampling the signals output from at least the image pickup element, and mixes in a predetermined ratio based on the comparison result the white balance control signal for white balance adjustment generated by the first white balance adjusting means using the output signal from the image pickup element and the white balance control signal for white balance adjustment generated by the second white balance adjusting means using the output signal from the colorimetric sensor excluding the image pickup element. White balance adjustment is performed based on the output signal from the synthesizing means, and an image pickup operation is performed. There is thus provided an image pickup device in which appropriate white balance adjustment can be performed under a photographic condition, that is, both under a photographic condition not suitable for the outdoor metering mode (for example, during distance adjustment, changes in lighting conditions, backlighting or a dark background) and under a photographic condition not suitable for the TTL mode (for example, during a monochrome full-frame image or a large influence of a monochrome object color), and at the same time an appropriate effect is achieved, as opposed to eliminating the advantages of both of the known methods as well as the additional known method.

In the arrangement including the storage device for storing the white balance control voltages of the first and second white balance adjusting devices for carrying out an appropriate white balance adjustment by means of the stored white balance control voltages, the white balance control voltages stored in the storage device are used for carrying out an optimal white balance adjustment when the white balance adjustment cannot be carried out correctly in a normal manner.

An image pickup device is provided to perform appropriate white balance adjustment under different conditions.

According to the present invention, control is not based on the colors or brightness levels of the object, but on a difference between sample data. If the invention is used in a Switching operation within the scope of white balance control, then an influence of a light source color can be eliminated in detail to accurately detect whether a frame is a monochrome frame, thereby achieving more precise white balance control.

Claims (20)

1. Image recording device, with (a) an image recording device for forming a video signal from an object light, (b) extracting means for extracting a video signal at a plurality of predetermined different areas in a frame to form a plurality of extracted information, (c) a comparison device for comparing the plurality of extracted information with each other to output a plurality of comparison results, and (d) a white balance device for adjusting a white balance of a complete frame of the video signal using many of the plurality of comparison results. 2. An image pickup device according to claim 1, comprising a second white balance adjusting means for generating a control signal for white balance adjustment using a signal output from a color temperature sensor excluding the image pickup means, and a synthesizing means for setting and outputting a variable synthesis ratio of the control signal of the first and second white balance adjusting means in response to information of an optical system. 3. Apparatus according to claim 2, wherein the information of the optical system is information of a the image capture device and an object. 4. The apparatus according to claim 2, wherein the information of the optical system is information of a focal length of the optical image pickup system. 5. The apparatus according to claim 2, wherein the optical system information represents information of a distance measuring device for measuring a distance between the image pickup device and an object, and information regarding a focal length of the optical image pickup system. 6. An image pickup device according to claim 1, comprising second white balance adjusting means for generating a control signal for white balance adjustment using a signal output from a color temperature sensor excluding the image pickup element, and synthesizing means for comparing a color temperature information ratio of the image pickup element with a color temperature information ratio of the color temperature sensor and setting and outputting a variable synthesis ratio of the control signal of the first and second white balance adjusting means. 7. Apparatus according to claim 6, further comprising a warning device pur generating a photographic warning signal. 8. An apparatus according to claim 6, further comprising a storage means for storing the white balance control voltages of the first and second white balance adjusting means, wherein a white balance adjustment is performed using the stored white balance control voltages. 9. An image pickup device according to claim 1, comprising second white balance adjustment means for generating a control signal for white balance adjustment using a signal output from a color temperature sensor, and synthesizing means for variably setting a synthesis ratio of the control signal depending on a difference between the signal output from the image pickup device or an equivalent signal thereto and the signal output from the color temperature sensor. 10. An image pickup device according to claim 1, comprising a second white balance adjustment device for generating a control signal for white balance adjustment using a signal output from a color temperature sensor having a frame angle different from an image pickup angle of an image pickup optical system, and a synthesizer for comparing an output signal of a photometric device different from the color temperature sensor with the output signal of the color temperature sensor and for variably outputting the two control signals. 11. An apparatus according to claim 10, wherein the photometric device has a photometric angle of view that is approximately equal to the image pickup angle of the optical image pickup system. 12. An apparatus according to claim 10, wherein the photometric device has a photometric angle of view that is smaller than the image pickup angle of the image pickup optical system. 13. An apparatus according to claim 10, wherein the photometric device uses an image pickup element. 14. An image pickup device according to claim 1, comprising second white balance adjusting means for generating a white balance control signal for white balance adjustment using an output signal output from a color temperature sensor excluding the image pickup element, and synthesizing means for comparing signals from predetermined portions on a frame after sampling the signals output from at least the image pickup element, and for mixing the white balance control signals of the first and second white balance adjusting means in a predetermined ratio depending on a comparison result. 15. Apparatus according to claim 14, further comprising a warning device for generating a photographic warning signal. 16. An apparatus according to claim 14, further comprising a storage means for storing the white balance control voltage of the first and second white balance adjusting means, wherein a white balance adjustment is performed using the stored white balance control voltages. 17. An image pickup device according to claim 1, comprising second means for generating a second white balance control signal based on an image pickup light obtained in a different state from the image pickup light used in the first means, and control signal generating means for synthesizing the first and second white balance control signals depending on an image pickup condition and generating a third white balance control signal. 18. Apparatus according to claim 17, wherein the second device generates the second white balance control signal based on the output signal of an external photometric sensor, 19. An apparatus according to claim 17, wherein said second means generates a white balance control signal based on an image pickup light range larger than that of said first means. 20. The apparatus according to claim 17, wherein the image pickup condition includes a color deviation of the image pickup light.